This invention relates to high resolution raster display systems and particularly to an analog display circuit including a wideband amplifier circuit for use in such a system.
There exists, in the prior art, a variety of systems for displaying data, including systems for direct viewing of a cathode ray tube (CRT), systems for projection viewing of a CRT, and flat screen systems (e.g., LED displays, plasma display panels, flat CRT panels, etc.). In addition, different systems exist for generating the display for use in a particular display system. These display generation systems include raster scan display systems and stroke writer systems.
Recently, there has been an increased concern with air safety and, in particular, with the quality of air traffic control. This has lead to a study of the air traffic control equipment presently being used, and particularly the displays used in such equipment. It has been found that this equipment should be improved and made uniform. In an effort to update the air traffic control system in the United States, the FAA is seeking to provide air traffic control work stations which are standardized to have a 20".times.20" display of at least 2000 by 2000 pixels (where a pixel is defined as the smallest addressable dot which can be displayed on a screen). The FAA has also required that these displays be capable of providing shaded background areas and a color display.
Displays used in air traffic control have traditionally used stroke writer technology which is capable of providing clear, flicker-free presentations of lines and characters at acceptable brightness levels. However, with this type of display system, it is difficult to provide shaded background areas and to provide a color display. In particular, in order to provide shaded areas on the display, a high power deflection system would be required to move the beam fast enough to create a shaded area. In addition, it would b necessary to provide new equipment in order to generate a color display.
In contrast to stroke writer systems, raster display systems (e.g., standard television) consume relatively less power, have no background shading problem, and currently are capable of providing a color display. However, currently available raster displays are not capable of providing the large viewing area and high resolution required for certain applications, including the large screen, high resolution requirements of the FAA.
At present, commercial television provides 525 horizontal lines which are interlaced 2 to 1, with a 30 hertz refresh cycle. In addition, there are approximately 300 pixels per horizontal line on the display. Thus, the requirement of a display of 2000 lines by 2000 pixels imposes substantially greater data handling requirements on the display system than does commercial television.
Today, a high quality raster display is capable of providing 1280 by 1024 pixels and requires 100 to 120 MHz video bandwidth (as opposed to the commercial broadcast video bandwidth which is approximately 3 MHz). In contrast, the provision of a display of 2048 by 2048 pixels (rounding the 2000.times.2000 pixel requirement to a power of 2), interlaced 2 to 1, with a refresh cycle of 40 hertz, requires a video bandwidth of approximately 210 MHz.
In addition to the FAA requirements, it is desirable that an air traffic control display have high resolution as well as the capability of displaying various characteristics (e.g., weather, data, flight path, emergency situations, map area, etc.) in a flexible manner which can be altered by an operator who is viewing the display, thereby providing the operator an opportunity to more clearly interpret the data being displayed by adjusting the relative intensity of selected portions of the display. This type of flexible display would also allow an air traffic controller to clarify what he or she sees on the display and to obtain a better view of particular portions of the display (e.g., by brightening or dimming certain display features) in an effort to clarify the image as seen by the operator.
In addition to the need for the above-discussed type of display for use in air traffic control work stations, there is a general need in the display art for large, high resolution displays for use in a variety of industries. For example, such high resolution displays would be advantageous for use as monitors in the fields of computer graphics, CAD/CAM, medicine, defense and other fields.
Therefore, there is a need in the display art, for circuitry capable of processing digital image data at a high data rate in order to provide the processed image data as display signals for use in a high resolution raster scan display system. There is also a need for such processing circuitry which allows certain attributes of the display to be programmable, so that the display can be programmed to display different types of features as required for different types of displays. Further, there is a need for analog display circuitry which is capable of receiving the high speed display signals and driving high resolution raster displays. There is also a need for analog circuitry which is capable of changing the relative display intensities of certain features of the display.